Electric heating element



April 7, 1964 L. E. FENN ELECTRIC HEATING ELEMENT Filed July 10, 1955 Ro 9. mm F 3 w 3 5 M 6 e m H m 8 w N a a z a f 2 U G F QR W 2 v w. 8% w WA fl U n H g n w; a E A w fl H m y 3 m 2 ATTORNEYS United States Patent3,127,666 ELECTRHQ HEATING ELEMENT Lawrence Fenn, Bridgeport, Conn,assignor to Case!) Produem Corporation, Bridgeport, Conn, a corporationof Connecticut Filed July 10, 1953, Ser. No. 367,233 6 Claims. (Ci.29--155.e2)

,T'his invention relates to electric cigar lighters, and particularly tolow-voltage heating elements for cigar lighters of the type commonlyused in automobiles, boats and aircraft.

For many years pleasureautomobile electric systems have beenstandardized as .to voltage, operating at substantially six volts asobtained from a three-cell lead-acid storage battery.

Electric cigar lighters for six-volt use in pleasure cars have compriseda tubular holder and a plug-like igniting unit receivable in the holderand removable therefrom for use, said igniting unit having at its innerend an economically produced heating coil formed of flat metal ribbonwound in a pancakeshaped spiral with air-spaced turns, said coil beingmounted in a shallow metal cup of slightly less diameter than thetubular holder.

Commercial vehicles having 12-volt electric systems, and aircraft with24-volt systems have in the past been supplied with cigar lighterswherein a more costly heating coil was used, having more turns of ribbonof thinner cross section and greater length, the coil being permeatedwith a ceramic cement which, when it hardened, supported the coil andinsured proper spacing of the turns and freedom from short circuit andburn out. Such coils, in addition to being more costly, sometimes faileddue to the unequal expansion in the coil loosening the ceramic andpermitting it to fall out.

It is now proposed to standardize pleasure-car electric systems attwelve volts, requiring that the present econominal and highlysatisfactory six-volt heating coil be altered to accommodate the highervoltage by the use of ribhon of thinner cross section or greater length,or both. Such an altered coil wound in the customary manner and withoutthe ceramic support cannot be readily used with the existing mountingcup since the added length and lesser thickness render it mechanicallyunstable to the extent that it loses its fiat shape and also since theadjacent turns easily touch and short-circuit each other, burning outthe coil.

An object of the present invention is to provide an improved, economicaland highly satisfactory low-voltage heating coil for cigar lighters ofautomobiles, boats, airoraft and the like, which coil can be readilyused with existing holder and igniting plug structures, including theshallow metal mounting cup for the coil, without the turns of the coileasily short-circuiting and burning out.

Another object of the invention is to provide an improved low-voltageheating coil as above set forth, which is mechanically strong andself-supporting, doing away with the necessity of seperate or additionalsupporting means such as ceramic cement, etc.

A further object of the invention to provide an improved low-voltageheating coil in accordance with the above which may be readily andeconomically produced, and which will be reliable in use and capable ofmany cycles of operation.

Yet another object of the invention is to provide an improvedlow-voltage heating coil as above set forth, which will withstandlimited over-voltages to an appreciable extent and for an appreciabletime before burning out.

A still further object of the invention is to provide an improvedlow-voltage heating coil for a. cigar lighter,

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which will retain its igniting heat for a relatively long time.

Further objects of the invention include the provision of improvedmethods for producing heating coils as set forth above.

Other features and advantages will hereinafter appear.

In the accompanying drawings:

FIGURE 1 is a side elevational View of a cigar lighter igniting unit,and a vertical axial section of part of the holder, the heating elementof the igniting unit, as made in accordance with the invention, beingshown in vertical section.

FIG. 2 is an end elevational view of the igniting unit, showing theimproved heating coil of the invention.

FIG. 3 is a plan view of a heating coil during its fabrication, after ithas been wound and confined against unwinding, this figure illustratinga step in the method of the invention.

FIG. 4 is a fragmentary sectional view taken on line 4-4- of FIG. 3.

FIG. 5 is a plan view of a heating coil after being wound and confined,showing a different kind of confining means.

FIG. 6 is a diagrammatic view illustrating the annealing step in themethod of forming heating coils according to the invention.

FIG. 7 is a diagrammatic view of a circuit used to carry out steps inthe method of the invention, relating to oxidizing and insulating theheating coil.

FIG. 8 is a vertical sectional view of an annealing furnace, used as analternative to the high frequency heating apparatus shown in FIG. 6.

H6. 9 is a diagrammatic view showing another apparatus by whichoxidizing and insulating of the coil is accomplished.

The cigar lighter illustrated in FIGS. 1 and 2 comprises a holdingdevice 1d consisting of a tubular metal shell 11 and a clamping sleeve12 by which the shell 11 is attached to a supporting panel 13.

Receivable in the holder It) for storage and energization is a plug-likeigniting unit 14 comprising a cylindrical body 15 having a manuallyengageable knob 1.6 and having a friction sleeve 17 by which theigniting unit is frictionally supported in the shell 11.

At its inner end the igniting unit 14 has a heating element assemblycomprising a supporting thimble 18 removably secured to the body 15 bybeing threaded thereinto, comprising a shallow metal contact cup 19attached to the thimble 18 and constituting a mounting and contact for apancake-shaped heating coil 20.

In accordance with the present invention an improved method is providedfor fabricating the heating coil, and a novel and improved heating coil24) is provided for low-voltage applications such as in automobiles,boats or aircraft, the said heating coil being economical to fabricateand resistant to short-circuiting of the turns and burning out while atthe same time being tightly wound withthe turns in intimate contact withand adhered to each other, being mechanically strong and selfsupportingwithout the use of separate or additional supporting means such asceramic cement, etc., being reliable in useand capable of many cycles ofoperation and also capable of withstanding limited over-voltages, andbeing capable of retaining an igniting temperature for a relatively longtime after its energization has been terminated. My improved heatingcoil is shown as being formed of flat metal alloy ribbon tightly woundin a pancake shape with adjacent turns in intimate contact but insulatedfrom each other, the entire coil being rigid as to relative movementbetween its turns and thereby constituting a unitary structure whichwill hold its shape under all normal conditions of use. In forming thecoil 24) I use a heat-resistant alloy having an appreciable aluminumcontent. One example of such alloy, known commercially as Kanthal D,consists of 3 /2 aluminum, 23% chromium, 2% cobalt and 71 %1 iron..Variations in the proportions of these elements are possible. Forexample, the aluminum may vary from 3 /2 to 6 percent, the chromiumfrom, 20 to 25' percent and the cobalt from 1 to 3 percent, and otherproportions and alloys have also beenfound suitable. As a furtherillustration, an alloy of 6% aluminum, 20% chromium and 74% iron issuitable for the purposes of the present invention.

In carrying out the process of'theinventionby which my improved heatingcoil is produced, I wind a fiat ribbon of suitable metal alloy into theshape of a tight spiral, such a coil being indicated at 29a in FIG. 3.Where the coil is to be used with alZ-volt supply, it may have aresistance of 1.66 ohms and be 18" long, .010" thick and wide. While thecoil Ztia is still tightly wound it is placed in a retainer ring 21which confines the coil and prevents it from unwinding.

The ring 21, see FIG. 4, may advantageously be formed of drawn sheetmetal a channel-shaped cross section, having an outer, main or a bodyportion 22, an inner coil-contacting portion 23 spaced inwardly from thebody portion 22 and a connector portion 24 spanning the space betweenthe portions 22 and 23. The advantage of this particular construction ofthe retainer 21 will be brought out later.

After the coil Zita has been wound and confined in the retainer 21 Isubject it to an annealing heat by which the flat ribbon is annealed orrelieved of temper caused by work-hardening incurred during itsfabrication and coiling. I have found that a suitable temperature forannealing the coil Zlla is in the neighborhood of 1500 F.

The annealing of the coil 26a may be done by a high frequency electricfield, in' an arrangement such as that shown in FIG. 6. In this figure asupply of high frequency energy 25 is connected to a field-concentratingcoil or helix, through which a conveyor belt 27 passes. The heatingcoils 26a which are to be annealed are placed on the conveyor belt 27and passed through the coil 26, and are discharged from the right-mostend of the conveyor 27 in annealed condition. Where the coils 20a areconfined by the retainers 21, the latter will also be heated by the highfrequency field and will supply heat to the coils and facilitate theannealing thereof. Due to the thin cross section and relatively smallmass of the retainers 21, as accomplished by their drawn sheet-metalconstruction, they will not heat abnormally fast, to the point ofmelting prior to complete annealing of the coil 20a, provided that thecycle of heating is not made too short. As an alternative to theretainer 21 I may provide a retainer 28, see FIG. 5, of nonmetallicmaterial such as ceramic composition, having lugs 29 which engage andconfine the spirally-formed heating coil, shown in FIG. ascoil b. Wherea ceramic retainer is employed, the annealing of the coil may proceedwithout regard to heating or melting of the retainer, obviously.

It will be understood that in place of the high frequency heating unitshown in FIG. 6 any other suitable annealing means may be employed, suchas an electric furnace 30 shown in FIG. 8 in which the heating coils 20aare supported on a removable tray 31.

After the coil 20a has been annealed it can be removed from confinementwithout losing substantially the initial coiled shape, the coilexpanding but little, if any, upon removal from the retainer 21. I havefound that in a properly annealed coil there remains but little forcebetween adjacent turns, all turns however remaining in contact with eachother and under some pressure. The importance and advantage of this'willbe brought out in detail later.

The annealed coil 20a is now ready for another step in my novel method,that of insulating the adjacent contacting turns from-each other andsecuring them to each other. This I accomplish by an oxidizing process.I prefer to carry out this process after the heating coil Zita has beenincorporated in the heating element assembly such as is shown in FIGS. 1and 2. The spiral coil 29 in such assembly has its inner end welded to asupporting and current-conducting central stud 32 and its outer endoutwardly offset and welded to the inner wall of the contact cup 19. Insuch assembly electrical connection obviously may be readily efiected tothe ends of the coil 24%. The coil is now placed in a circuit such asthat illustrated in FIG. 7, wherein the stud 32 is connected by a Wire33 to a battery 34 which is in turn connected by a wire 35 to a slidingcontact 36 engageable selectively with button contacts 37, 38,739, wand41 joined respectively to resistors 42, 43, 44, 45 and 46 whose otherends are connected to a wire 47 leading to the contact cup 19 of theheating coil assembly. The resistors 42, 43, 44, 4-5 and .46 togetherwith the sliding contact 36 enable currents of diiferent intensities tobe passed through-the heatingcoilZt. Where the heating coil 26 isintended for twelve-volt use I subject it to a potential of eight voltsfor an interval of 20 seconds, as by moving the slidable contact 36 inengagement with the contact button 3'7. I then terminate thisenergization and next subject the coil 24 to a potential of ten voltsfor 15 seconds by moving the sliding contact 36 in engagement with thecontact button 38. I then terminate this ene'rgization and subject thecoil 25) to a potential of twelve volts for 10 seconds by moving thesliding contact 36 in engagement with the contact button 39. ThereafterI terminate this energization and subject the coil 24 to a potential ofthirteen volts for 10 sec onds by moving the sliding contact 36 inengagement with the contact button 4-9. I terminate this energizationand then repeat it, and thereafter I subject the coil 29 to a potentialof fourteen volts for 10 seconds by moving the sliding contact 35' inengagement with the contact button ill.

I have found that by energizing the heating coil 20 as above outlined analuminum oxide coating will be formed on the ribbon and at the same timeappreciable shortcircuiting between turns will be prevented. Thereforethe coil 2% will not burn out during the oxidizing procedure, and theoxide which is formed will insulate the adjacent contacting convolutionsfrom each other, and the oxide coatings will adhere to each other,rendering the turns of the coil relatively immovable under normalconditions of use. As a consequence, a unitary, solid, pancake-shapedcoil is produced wherein the adjacent turns are effectively insulatedand prevented from having relative movement and from becomingshort-circuited. The coil is therefore mechanically rigid and stable,and will not get out of shape during use as-would otherwise occur whereribbon of thin cross section is wound in an unsupported coil of a largenumber of turns. Be cause of the solid mass of the coil 29 and theabsence of air spaces between turns, the coil has excellent heatretention and will maintain an igniting temperature for a relativelylong period of time. I have found also that a coil constructed inaccordance with the above will withstand moderate over-voltages forlimited intervals of time without burning out. For example it willwithstand an energization of twelve volts for two minutes withoutburning out, and if subjected to thirteen volts will only burn out afterone minute and 54 seconds. When subjected to fourteen volts it willburn. out only after one minute and 19 seconds of energization. Ifsubjected to fifteen volts it will burn out after 45 seconds ofenergization. This performance is substantially better than theperformance of the conventional six-volt heating coil having spacedconvolutions which are out of contact with each other, since a six-voltcoil when subjected to seven volts will burn out in 57 seconds ascompared with the fourteen volt test wherein the twelve-volt coil lastsfor one minute and 19 seconds.

In FIG. 9 I show a heating coil 20 connected to a battery 48 through arheostat 49 by which diiferent voltages may be applied to the coil fordifferent intervals of time, as outlined above. This arrangement mightin some instances be more advantageous than the circuit found in FIG. 7.

While I have illustrated and described the construction, and the methodof producing an improved twelvevolt coil for a cigar lighter, it is tobe understood that twenty-four volt coils, or coils intended for otherlow voltages may be produced in a like manner. The improved heating coilof the present invention has been found to have an extremely long life,having withstood in excess of 20 thousand cycles of energization at 13.5volts without showing signs of deterioration or failure, each cycle ofenergization lasting for 12 seconds which is sufiicient to bring thecoil well up into the incandescent range required for lightingcigarettes, cigars, etc.

Variations and modifications may be made Within the scope of the claimsand portions of the improvements may be used without others.

I claim:

1. The method of making an electrical heating coil for a cigar lightercomprising the steps of Winding a flat, metal ribbon, formed of a metalalloy including iron and aluminum in its composition, into a tight,pancake-shape spiral with adjacent turns touching each other, confiningthe spiral to prevent appreciable unwinding and separation of the turns,heating the coil to relieve the winding strains and thereafter heatingthe coil sufliciently to form in situ an oxide on the surfaces of theribbon, said oxide providing electrical insulation on the surfaces ofthe wire to prevent short-circuiting between the turns of the coil andproviding mechanical adhesion between the contacting turns to preventrelative shifting thereof and axial deformation of the coil.

2. The method of making an electrical heating coil for use in alow-voltage cigar lighter, which includes the steps of winding a flatmetal ribbon, having a composition whose oxide is electricallyinsulating, into a tight, pancake-shaped spiral with adjacent turnstouching each other, confining the spiral to prevent appreciableunwinding and separation of the turns thereof, subjecting the coil toheat to anneal the coil, and thereafter passing heating currents throughthe coil in successive stages to oxidize the surfaces of the ribbon andprovide electrical insulation and mechanical adhesion between adjacentcontacting turns of the coil.

3. The method of making an electrical heating coil for use in alow-voltage cigar lighter, which includes the steps of winding a flatmetal ribbon, having a composition whose oxide is electricallyinsulating, into a tight, pancake-shaped spiral with adjacent turnstouching each other, confining the spiral to prevent appreciableunwinding and separation of the turns thereof, subjecting the coil toheat to anneal the coil, and thereafter passing a heating electricalcurrent of lesser value than the intended electrical heating currentthrough the coil to oxidize the surfaces of the ribbon and provideelectrical insulation and mechanical adhesion between adjacentcontacting turns of the coil.

4. The method of making an electrical heating coil for use in alow-voltage cigar lighter, which includes the steps of winding a fiatmetal ribbon, having a composition whose oxide is electricallyinsulating, into a tight, pancake-shaped spiral with adjacent turnstouching each other, confining the spiral to prevent appreciableunwinding and separation of the turns thereof, subjecting the coil toheat to anneal the coil, and thereafter passing successive heatingelectrical currents of lesser value than the intended electrical heatingcurrent through the coil to oxidize the surfaces of the ribbon andprovide electrical insulation and mechanical adhesion between adjacentcontacting turns of the coil.

5. The method of making an electrical heating coil for use in alow-voltage cigar lighter, which includes the steps of winding a flatmetal ribbon, having a composition Whose oxide is electricallyinsulating, into a tight, pancake-shaped spiral with adjacent turnstouching each other, confining the spiral to prevent appreciableunwinding and separation of the turns thereof, subjecting the coil toheat to anneal the coil, and thereafter passing successive heatingelectric currents of lesser value than the intended electrical heatingcurrent, but each successively greater than the preceding, through thecoil to oxidize the surfaces of the ribbon and provide electricalinsulation and mechanical adhesion between adjacent contacting turns ofthe coil.

6. The invention as defined in claim 5 in which the successive currentsof increasing value are maintained for intervals which are successivelylonger each than the preceding interval.

References Cited in the file of this patent UNITED STATES PATENTS515,280 Brown Feb. 20, 1894 1,946,434 Bach Feb. 6, 1934 2,062,701 CohenDec. 1, 1936 2,157,050 Bilger et a1. May 2, 1939 2,269,394 Cuno et a1Jan. 6, 1942 2,287,460 Wagenhals June 23, 1942 2,465,864 Freeman et a1.Mar. 29, 1949 2,585,037 Robinson et a1. Feb. 12, 1952 2,596,325 CernyMay 13, 1952 2,652,622 Charbonneau Sept. 22, 1953 2,702,935 Kyle Mar. 1,1955 2,975,262 Schnick Mar. 14, 1961 OTHER REFERENCES Woldman & Metzler:Engineering Alloys; 2nd Edition, 1945; published by American Society forMetals; page 200 (Copy in Div. 3).

Woldman: Engineering Alloys; 3rd Edition; 1954; published by AmericanSociety for Metals; pages 238, 810 (Copy in Div. 3).

1. THE METHOD OF MAKING AN ELECTRICAL HEATING COIL FOR A CIGAR LIGHTERCOMPRISING THE STEPS OF WINDING A FLAT, METAL RIBBON, FORMED OF A METALALLOY INCLUDING IRON AND ALUMINUM IN ITS COMPOSITION, INTO A TIGHT,PANCAKE-XHAPE SPIRAL WITH ADJACENT TURNS TOUCHING EACH OTHER, CONFININGTHE SPIRAL TO PREVENT APPRECIABLE UNWINDING AND SEPARATION OF THE TURNS,HEATING THE COIL TO RELIEVE THE WINDING STRAINS AND THEREAFTER HEATINGTHE COIL SUFFICIENTLY TO FORM IN SITUAN OXIDE ON THE SURFACES OF THERIBBON, SAID OXIDE PROVIDING ELECTRICAL INSULATION ON THE SURFACES OFTHE WIRE TO PREVENT SHORT-CIRCUITING BETWEEN THE TURNS OF THE COIL ANDPROVIDING MECHANICAL ADHESION BETWEEN THE CONTACTING TURNS TO PREVENTRELATIVE SHIFTING THEREOF AND AXIAL DEFORMATION OF THE COIL.